Process for the polymerization of olefins

ABSTRACT

A multistep process comprising the following steps:
         step a) polymerizing propylene and optionally one or more monomers selected from ethylene or alpha olefins of formula CH 2 ═CHT 1 , wherein T 1  is a C 2 -C 10  alkyl radical in the presence of a catalyst system supported on an inert carrier, comprising:
           ii) one or more metallocene compounds of formula (I):   
               

     
       
         
         
             
             
         
       
         
         
           
             
               
                 ii) an alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally 
                 iii) an organo aluminum compound; 
               
             
             step b) contacting, under polymerization conditions, in a gas phase, propylene or ethylene with one or more alpha olefins of formula CH 2 ═CHT, wherein T is hydrogen or a C 1 -C 10  alkyl radical, and optionally a non-conjugated diene, in the presence of the polymer obtained in step a) and optionally in the presence of an additional organo aluminum compound; provided that an homopolymer is not produced; 
             wherein: the compound of formula (I) is described in the application.

This application is the U.S. national phase of International ApplicationPCT/EP2006/060941, filed Mar. 22, 2006, claiming priority to EuropeanPatent Application 05102348.9 filed Mar. 23, 2005, and the benefit under35 U.S.C. 119(e) of U.S. Provisional Application No. 60/666,219, filedMar. 29, 2005; the disclosures of International ApplicationPCT/EP2006/060941, European Patent Application 05102348.9 and U.S.Provisional Application No. 60/666,219, each as filed, are incorporatedherein by reference.

The present invention relates to a multistep process for preparingheterophasic propylene copolymers, by using a particular class ofmetallocene compounds.

Multistep processes for the polymerization of olefins, carried out intwo or more reactors, are known from the patent literature and are ofparticular interest in industrial practice. The possibility ofindependently varying, in any reactors, process parameters such astemperature, pressure, type and concentration of monomers, concentrationof hydrogen or other molecular weight regulator, provides much greaterflexibility in controlling the composition and properties of the endproduct compared to single-step processes. Multistep processes aregenerally carried out using the same catalyst in the varioussteps/reactors. The product obtained in one reactor is discharged andsent directly to the next step/reactor without altering the nature ofthe catalyst. WO 01/48034 describes a class of bis indenyl metallocenecompounds wherein the indenyl moieties are substituted in position 4with a substituted aryl radical. This document exemplifies the use ofthis class of metallocene compounds in a multistage process.

PCT/EP2004/013827 relates to a class of bis indenyl metallocenecompounds wherein at least one indenyl moiety is substituted in position5 and 6 with a condensed ring. This documents describes in a genericalway a process for preparing an heterophasic polymer. It describes onlythe polymers that can be prepared in each stage without explaining howeach step has to be carried out. Moreover this document reports that theamount of copolymer produced in the second stage ranges from 3 to 60% byweight of the end product.

The applicant now surprisingly found that when a particular class of bisindenyl metallocene compounds is used for the preparation of anheterophasic polymer it is possible to achieve in high yield a polymerhaving an high molecular weight. In particular the rubber phase of theheterophasic polymer results to have a very high molecular weight.Moreover when the amount of the rubber exceeds a certain threshold it ispossible to obtain a soft final polymer with an optimum balance ofproperties.

Therefore an object of the present invention is a multistep processcomprising the following steps:

-   step a) polymerizing propylene and optionally one or more monomers    selected from ethylene or alpha olefins of formula CH₂═CHT¹, wherein    T¹ is a C₂-C₁₀ alkyl radical in the presence of a catalyst system    comprising:    -   i) one or more metallocene compounds of formula (I):

-   -   ii) an alumoxane or a compound capable of forming an alkyl        metallocene cation; and optionally    -   iii) an organo aluminum compound;

-   step b) contacting, under polymerization conditions, propylene or    ethylene with one or more alpha olefins of formula CH₂═CHT, wherein    T is hydrogen or a C₁-C₁₀ alkyl radical, and optionally a    non-conjugated diene, in the presence of the polymer obtained in    step a) and optionally in the presence of an additional organo    aluminum compound; provided that an homopolymer is not produced;    -   wherein the amount of the polymer obtained in step a) ranges        from 5% by weight to 39% by weight of the polymer obtained in        the whole process and the amount of polymer obtained in step b)        ranges from 61% by weight to 95% by weight of the polymer        obtained in the whole process;        wherein: in the compound of formula (I):        M is an atom of a transition metal selected from those belonging        to group 4 of the Periodic Table of the Elements; preferably M        is zirconium, titanium or hafnium;        X, equal to or different from each other, is a hydrogen atom, a        halogen atom, a R, OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group        wherein R is a linear or branched, cyclic or acyclic,        C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,        C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical; optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; and R′ is a C₁-C₂₀-alkylidene,        C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or        C₇-C₂₀-arylalkylidene radical; preferably X is a hydrogen atom,        a halogen atom, a OR′O or R group; more preferably X is chlorine        or a methyl radical;        L is a divalent bridging group selected from C₁-C₂₀ alkylidene,        C₃-C₂₀ cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene,        or a C₇-C₂₀ arylalkylidene radicals, optionally containing        heteroatoms belonging to groups 13-17 of the Periodic Table of        the Elements, or it is a silylidene radical containing up to 5        silicon atoms; preferably L is Si(R¹¹)₂ wherein R¹¹ is a linear        or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl,        C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or        C₇-C₄₀-arylalkyl radical; more preferably L is Si(CH₃)₂ or        SiPh₂;        R¹ and R¹⁹ are different from each other and are a Z^(1′) or        Z^(2′) group wherein Z^(1′) is an alpha branched C₁-C₂₀        hydrocarbon radical optionally containing heteroatoms belonging        to groups 13-17 of the Periodic Table of the Elements, and        Z^(2′) is a linear C₁-C₄₀ hydrocarbon radical optionally        containing heteroatoms belonging to groups 13-17 of the Periodic        Table of the Elements; with the proviso that if R¹ or R¹⁹ are        Z^(1′) then R¹⁹ or R¹ are Z^(2′); preferably Z^(1′) is a        compound of formula of formula (II)

or an alpha branched aryl or arylalkyl radical containing from 2 to 20carbon atoms optionally containing O, N, S, P and Se atoms, inparticular O, N and S atoms such as 2(5-Me-thiophenyl) or2(5-Me-furanyl) radicals;wherein in the compound of formula (II) R²³ and R²⁴, equal to ordifferent from each other, are C₁-C₄₀ hydrocarbon radicals optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably they are C₁-C₂₀ hydrocarbon radicalsoptionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements; more preferably R²³ and R²⁴ areC₁-C₂₀-alkyl, C₂-C₄₀ alkenyl, preferably C₂-C₂₀ alkenyl, C₂-C₄₀ alkynyl,preferably C₂-C₂₀ alkynyl radicals, optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements; morepreferably R²³ and R²⁴ are linear or branched C₁-C₁₀-alkyl radical suchas methyl, or ethyl radicals; R²⁵ is an hydrogen atom or it has the samemeaning of R²³ and R²⁴; more preferably R²⁵ is a hydrogen atom;preferably Z^(2′) is a linear C₁-C₂₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl radical, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements;preferably Z^(2′) is a linear C₁-C₁₀-alkyl radical; more preferablyZ^(2′) is a methyl, or ethyl radical;R² and R³, are part of 4-7 membered ring condensed to the benzene ringof the indenyl moiety;preferably a 5 or 6 membered ring; said ring optionally containingheteroatoms belonging to groups 13-16 of the Periodic Table of theElements preferably groups 15-16 of the Periodic Table of the Elements;the valence of each atom forming said ring being substituted with R¹⁸radicals; that means that is filled with R¹⁸ groups, wherein R¹⁸, equalto or different from each other, are hydrogen atoms or a C₁-C₄₀hydrocarbon radical; preferably R¹⁸ is a hydrogen atom or a linear orbranched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical,optionally containing one or more heteroatoms belonging to groups 13-17of the Periodic Table of the Elements; more preferably R¹⁸ is a hydrogenatom or a linear or branched, C₁-C₂₀-alkyl radical; more preferably R¹⁸is a hydrogen atom or a methyl or ethyl radical; said ring can besaturated or it can contain double bonds; preferably R² and R³, formtogether a condensed saturated 3-7 membered ring;R⁴ is a hydrogen atom or a C₁-C₄₀ hydrocarbon radical optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably R⁴ is a hydrogen atom or a linear orbranched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radicaloptionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements; preferably R⁴ is a hydrogen atom aC₁-C₁₀-alkyl or a C₆-C₄₀-aryl radical;W is an aromatic 5 or 6 membered ring that can contain heteroatomsbelonging to groups 15-16 of the Periodic Table of the Elements; thevalence of each atom of said ring is substituted with hydrogen atom orit can optionally be substituted with R⁵ groups, wherein R⁵, equal to ordifferent from each other, are C₁-C₄₀ hydrocarbon radicals optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably R⁵, are linear or branched, cyclic oracyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl, C₆-C₄₀-aryl,C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radicals optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements;Preferably W is selected from the group comprising the followingmoieties of formula (Wa), (Wb) and (Wc):

wherein the * represents the point in which the moiety bounds theindenyl moiety of the compound of formula (I);R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal to or different from each other, arehydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; preferably R⁶, R⁷, R⁸, R⁹ and R¹⁰, are hydrogen atoms orlinear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl,C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkylradicals optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements;Z¹ is a nitrogen atom or a CR¹⁰ group; Z² is a nitrogen atom or a CR⁶group; Z³ is a nitrogen atom or a CR⁷ group; Z⁴ is a nitrogen atom or aCR⁸ group; Z⁵ is a nitrogen atom or a CR⁹ group; provided that not morethat 2 groups among Z¹, Z², Z³, Z⁴ and a Z⁵ are nitrogen atoms,preferably not more that one group among Z¹, Z², Z³, Z⁴ and Z⁵ is anitrogen atom;Z⁶ is an oxygen atom, a sulfur atom, a NR¹³ group or a CR¹³ group; Z⁷ isan oxygen atom, a sulfur atom, a NR¹⁴ group or a CR¹⁴ group; Z⁸ is anoxygen atom, a sulfur atom, a NR¹⁵ group or a CR¹⁵group; Z⁹ is an oxygenatom, a sulfur atom, a NR¹⁶ group or a CR¹⁶ group;Z¹⁰ is a nitrogen atom or a carbon atom that bonds the indenyl moiety ofthe structure of formula (I); with the proviso that not more than 1group among Z⁶, Z⁷, Z⁸, Z⁹ or Z¹⁰ is a sulfur atom, an oxygen atom or anitrogen-containing group atom selected from NR¹³, NR¹⁴, NR¹⁵, NR¹⁶, anda nitrogen atom;R¹³, R¹⁴, R¹⁵, and R¹⁶, equal to or different from each other, arehydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; preferably R⁶, R⁷, R⁸, R⁹ and R¹⁰, are hydrogen atoms orlinear or branched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl,C₂-C₄₀ alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkylradicals optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; more preferably R⁶, R⁷, R⁸, R⁹ andR¹⁰ are hydrogen atoms, C₁-C₄₀-alkyl or C₆-C₄₀-aryl radicals;

In the moiety of formula (Wa), in a preferred embodiment, R⁷ is aC₁-C₄₀-alkyl radical, preferably a branched C₁-C₄₀-alkyl radical such asa tertbutyl radical, more preferably R⁷ is a branched C₁-C₄₀-alkylradical wherein the carbon atom in position alpha is a tertiary carbonatom and R⁶, R⁸, R⁹ and R¹⁰ are hydrogen atoms;

In a further preferred embodiment R¹⁰ and R⁸ are C₁-C₄₀-alkyl radicals,preferably they are linear C₁-C₄₀ alkyl radicals such as methyl radicalsand R⁷, R⁸ and R⁹ are hydrogen radicals:

In a further preferred embodiment R⁶, R⁷ and R⁸ are linear or branchedC₁-C₄₀-alkyl radicals such as methyl or tertbutyl radicals and R¹⁰ andR⁹ are hydrogen atoms.

In a further preferred embodiment R⁶, R⁷, R⁸, R⁹ and R¹⁰ are hydrogenatoms;

In the moiety of formula (Wb), in a preferred embodiment, Z¹ is anitrogen atom and Z², Z³, Z⁴ and Z⁵ are respectively CR⁶, CR⁷, CR⁸ andCR⁹ wherein the meaning of R⁶, R⁷, R⁸, and R⁹ is described above; in afurther preferred embodiment Z³ is a nitrogen atom and Z¹, Z², Z⁴ and Z⁵are respectively CR¹⁰, CR⁶, CR⁸ and CR⁹ wherein the meaning of R¹⁰, R⁶,R⁸, and R⁹ is described above; in a further preferred embodiment Z² is anitrogen atom and Z¹, Z³, Z⁴ and Z⁵ are respectively CR¹⁰, CR⁷, CR⁸ andCR⁹ wherein the meaning of R¹⁰, R⁷, R⁸, and R⁹ is described above;

In the moiety of formula (Wc) in a preferred embodiment Z⁶ is an oxygenatom, a sulfur atom, a NR¹⁶ group; preferably it is a sulfur atom or aNR¹⁶; wherein R¹⁶ is preferably a C₁-C₄₀-alkyl radical; more preferablyZ⁶ is a sulfur atom; and Z⁷, Z⁸, Z⁹ and Z¹⁰ are respectively a CR¹⁴,CR¹⁵, CR¹⁶ and a carbon atom, wherein R¹⁴ is a hydrogen atom or aC₁-C₄₀-alkyl radical such as methyl or ethyl; and R¹⁵ and R¹⁶ arehydrogen atoms or C₁-C₄₀-alkyl radicals;

R²⁰, R²¹ and R²², equal to or different from each other, are hydrogenatoms or C₁-C₄₀ hydrocarbon radicals optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements;preferably R²⁰ and R²¹ are hydrogen atoms or C₁-C₁₀ alkyl radicals, withthe proviso that they are not both C₁-C₁₀ alkyl radicals; preferably R²²is an hydrogen atom;Preferred class of compounds of formula (I) have formula (III)

Wherein M, L, X, R¹, R⁴, R¹⁴, R¹⁵, R¹⁶, R¹⁹, R²⁰, R²¹, R²² and have themeaning reported above and R¹¹ and R¹², equal to or different from eachother, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; preferably R¹¹ and R¹² are hydrogen atoms or linear orbranched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl radicals, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements; more preferably R¹¹ and R¹²are hydrogen atoms or C₁-C₂₀-alkyl radicals such as methyl or ethylradicals.

A further preferred class of compounds of formula (I) have formula (IV)

Wherein M, L, X, R¹, R⁴, R⁶, R⁷, R⁸, R⁹, R¹⁰, R¹⁹, R²⁰, R²¹, R²² and Whave the meaning reported above and R¹¹ and R¹², equal to or differentfrom each other, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicalsoptionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements; preferably R¹¹ and R¹² are hydrogenatoms or linear or branched, cyclic or acyclic, C₁-C₂₀-alkyl, C₂-C₄₀alkenyl, C₂-C₄₀ alkynyl radicals, optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements; morepreferably R¹¹ and R¹² are hydrogen atoms or C₁-C₁₀-alkyl radicals suchas methyl or ethyl radicals; Preferably W is a moiety of formula (Wa) asdescribed above.

Compounds of formula (I) can be prepared according to PCT/EP2004/013827.

Alumoxanes used as component ii) in the catalyst system according to thepresent invention can be obtained by reacting water with anorgano-aluminium compound of formula H_(j)AlU_(3-j) or H_(j)Al₂U_(6-j),where the U substituents, same or different, are hydrogen atoms, halogenatoms, C₁-C₂₀-alkyl, C₃-C₂₀-cyclalkyl, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl orC₇-C₂₀-arylalkyl radicals, optionally containing silicon or germaniumatoms, with the proviso that at least one U is different from halogen,and j ranges from 0 to 1, being also a non-integer number. In thisreaction the molar ratio of Al/water is preferably comprised between 1:1and 100:1.

The alumoxanes used in the catalyst system according to the inventionare considered to be linear, branched or cyclic compounds containing atleast one group of the type:

wherein the substituents U, same or different, are defined above.

In particular, alumoxanes of the formula:

can be used in the case of linear compounds, wherein n¹ is 0 or aninteger of from 1 to 40 and the substituents U are defined as above; oralumoxanes of the formula:

can be used in the case of cyclic compounds, wherein n² is an integerfrom 2 to 40 and the U substituents are defined as above.

Examples of alumoxanes suitable for use according to the presentinvention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO),tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO),tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) andtetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

Particularly interesting cocatalysts are those described in WO 99/21899and in WO01/21674 in which the alkyl and aryl groups have specificbranched patterns. Non-limiting examples of aluminium compounds that canbe reacted with water to give suitable alumoxanes (b), described in WO99/21899 and WO01/21674, are: tris(2,3,3-trimethyl-butyl)aluminium,tris(2,3-dimethyl-hexyl)aluminium, tris(2,3-dimethyl-butyl)aluminium,tris(2,3-dimethyl-pentyl)aluminium, tris(2,3-dimethyl-heptyl)aluminium,tris(2-methyl-3-ethyl-pentyl)aluminium,tris(2-methyl-3-ethyl-hexyl)aluminium,tris(2-methyl-3-ethyl-heptyl)aluminium,tris(2-methyl-3-propyl-hexyl)aluminium,tris(2-ethyl-3-methyl-butyl)aluminium,tris(2-ethyl-3-methyl-pentyl)aluminium,tris(2,3-diethyl-pentyl)aluminium,tris(2-propyl-3-methyl-butyl)aluminium,tris(2-isopropyl-3-methyl-butyl)aluminium,tris(2-isobutyl-3-methyl-pentyl)aluminium,tris(2,3,3-trimethyl-pentyl)aluminium,tris(2,3,3-trimethyl-hexyl)aluminium,tris(2-ethyl-3,3-dimethyl-butyl)aluminium,tris(2-ethyl-3,3-dimethyl-pentyl)aluminium,tris(2-isopropyl-3,3-dimethyl-butyl)aluminium,tris(2-trimethylsilyl-propyl)aluminium,tris(2-methyl-3-phenyl-butyl)aluminium,tris(2-ethyl-3-phenyl-butyl)aluminium,tris(2,3-dimethyl-3-phenyl-butyl)aluminium,tris(2-phenyl-propyl)aluminium,tris[2-(4-fluorophenyl)-propyl]aluminium,tris[2-(4-chloro-phenyl)-propyl]aluminium,tris[2-(3-isopropyl-phenyl)-propyl]aluminium,tris(2-phenyl-butyl)aluminium, tris(3-methyl-2-phenyl-butyl)aluminium,tris(2-phenyl-pentyl)aluminium,tris[2-(pentafluorophenyl)-propyl]aluminium,tris[2,2-diphenyl-ethyl]aluminium andtris[2-phenyl-2-methyl-propyl]aluminium, as well as the correspondingcompounds wherein one of the hydrocarbyl groups is replaced with ahydrogen atom, and those wherein one or two of the hydrocarbyl groupsare replaced with an isobutyl group.

Amongst the above aluminium compounds, trimethylaluminium (TMA),triisobutylaluminium (TIBA), tris(2,4,4-trimethyl-pentyl)aluminium(TIOA), tris(2,3-dimethylbutyl)aluminium (TDMBA) andtris(2,3,3-trimethylbutyl)aluminium (TTMBA) are preferred.

Non-limiting examples of compounds able to form an alkylmetallocenecation are compounds of formula D⁺E⁻, wherein D⁺ is a Brønsted acid,able to donate a proton and to react irreversibly with a substituent Xof the metallocene of formula (I) and E⁻ is a compatible anion, which isable to stabilize the active catalytic species originating from thereaction of the two compounds, and which is sufficiently labile to beremoved by an olefinic monomer. Preferably, the anion E⁻ comprises oneor more boron atoms. More preferably, the anion E⁻ is an anion of theformula BAr₄ ⁽⁻⁾, wherein the substituents Ar which can be identical ordifferent are aryl radicals such as phenyl, pentafluorophenyl orbis(trifluoromethyl)phenyl. Tetrakis-pentafluorophenyl borate isparticularly preferred compound, as described in WO 91/02012. Moreover,compounds of formula BAr₃ can be conveniently used. Compounds of thistype are described, for example, in the International patent applicationWO 92/00333. Other examples of compounds able to form analkylmetallocene cation are compounds of formula BAr₃P wherein P is asubstituted or unsubstituted pyrrol radical. These compounds aredescribed in WO01/62764. Compounds containing boron atoms can beconveniently supported according to the description of DE-A-19962814 andDE-A-19962910. All these compounds containing boron atoms can be used ina molar ratio between boron and the metal of the metallocene comprisedbetween about 1:1 and about 10:1; preferably 1:1 and 2.1; morepreferably about 1:1.

Non limiting examples of compounds of formula D⁺E⁻ are:

-   Tributylammoniumtetra(pentafluorophenyl)aluminate,-   Tributylammoniumtetra(trifluoromethylphenyl)borate,-   Tributylammoniumtetra(4-fluorophenyl)borate,-   N,N-Dimethylbenzylammonium-tetrakispentafluorophenylborate,-   N,N-Dimethylhexylamonium-tetrakispentafluorophenylborate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate,-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)aluminate,-   N,N-Dimethylbenzylammonium-tetrakispentafluorophenylborate,-   N,N-Dimethylhexylamonium-tetrakispentafluorophenylborate,-   Di(propyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Di(cyclohexyl)ammoniumtetrakis(pentafluorophenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate,-   Triphenylcarbeniumtetrakis(pentafluorophenyl)aluminate,-   Ferroceniumtetrakis(pentafluorophenyl)borate,-   Ferroceniumtetrakis(pentafluorophenyl)aluminate.-   Triphenylcarbeniumtetrakis(pentafluorophenyl)borate, and-   N,N-Dimethylaniliniumtetrakis(pentafluorophenyl)borate.

Organic aluminum compounds used as compound iii) are those of formulaH_(j)AlU_(3-j) or H_(j)Al₂U_(6-j) as described above.

The catalysts system to be used in the process of the present inventioncan be supported on an inert carrier. This is achieved by depositing themetallocene compound i) or the product of the reaction thereof with thecomponent ii), or the component ii) and then the metallocene compound i)on an inert support. The support can be a porous solid such as talc, asheet silicate, an inorganic oxide or a finely divided polymer powder(e.g. polyolefin). Suitable inorganic oxides may be found among theoxides of elements of groups 2, 3, 4, 5, 13, 14, 15 and 16 of thePeriodic Table of the Elements. Examples of oxides preferred as supportsinclude silicon dioxide, aluminum oxide, and also mixed oxides of theelements calcium, aluminum, silicon, magnesium or titanium and alsocorresponding oxide mixtures, magnesium halides, styrene/divinylbenzenecopolymers, polyethylene or polypropylene. Other inorganic oxides whichcan be used alone or in combination with the abovementioned preferredoxidic supports are, for example, MgO, ZrO₂, TiO₂ or B₂O₃.

A suitable class of supports which can be used is that constituted byporous organic supports functionalized with groups having activehydrogen atoms. Particularly suitable are those in which the organicsupport is a partially crosslinked styrene polymer. Supports of thistype are described in European application EP-633 272.

Another class of inert supports particularly suitable for use accordingto the invention is that of polyolefin porous prepolymers, particularlypolyethylene.

A further suitable class of inert supports for use according to theinvention is that of porous magnesium halides such as those described inInternational application WO 95/32995.

The support materials used preferably have a specific surface area inthe range from 10 to 1 000 m²/g, a pore volume in the range from 0.1 to5 ml/g and a mean particle size of from 1 to 500 μm. Preference is givento supports having a specific surface area in the range from 50 to 500m²/g, a pore volume in the range from 0.5 to 3.5 ml/g and a meanparticle size in the range from 5 to 350 μm. Particular preference isgiven to supports having a specific surface area in the range from 200to 400 m²/g, a pore volume in the range from 0.8 to 3.0 ml/g and a meanparticle size of from 10 to 300 μm.

The inorganic support can be subjected to a thermal treatment, e.g. toremove adsorbed water. Such a drying treatment is generally carried outat from 80 to 300° C., preferably from 100 to 200° C., with drying atfrom 100 to 200° C. preferably being carried out under reduced pressureand/or a blanket of inert gas (e.g. nitrogen), or the inorganic supportcan be calcined at from 200 to 1000° C. to produce the desired structureof the solid and/or set the desired OH concentration on the surface. Thesupport can also be treated chemically using customary desiccants suchas metal alkyls, preferably aluminum alkyls, chlorosilanes or SiCl₄, orelse methylaluminoxane. Appropriate treatment methods are described, forexample, in WO 00/31090.

The inorganic support material can also be chemically modified. Forexample, treatment of silica gel with (NH₄)₂SiF₆ leads to fluorinationof the silica gel surface, or treatment of silica gels with silanescontaining nitrogen-, fluorine- or sulfur-containing groups leads tocorrespondingly modified silica gel surfaces.

Organic support materials such as finely divided polyolefin powders(e.g. polyethylene, polypropylene or polystyrene) can also be used andare preferably likewise freed of adhering moisture, solvent residues orother impurities by means of appropriate purification and dryingoperations before use. It is also possible to use functionalized polymersupports, e.g. supports based on polystyrene, via whose functionalgroups, for example ammonium or hydroxy groups, at least one of thecatalyst components can be immobilized. The solid compound obtained bysupporting the catalyst system object of the present invention on acarrier in combination with the further addition of the alkylaluminiumcompound either as such or prereacted with water if necessary, can beusefully.

Preferably step a) further comprises a prepolymerization step a-1).

The prepolymerization step a-1) can be carried out by contacting thecatalyst system with ethylene propylene or one or more alpha olefins offormula CH₂═CHT¹, wherein T¹ is a C₂-C₂₀ alkyl radical. Preferably saidalpha olefins are propylene or ethylene, at a temperature ranging from−20° C. to 70° C., in order to obtain a prepolymerized catalyst systempreferably containing from 5 to 500 g of polymer per gram of catalystsystem.

Thus preferably step a) comprises

a-1) contacting the catalyst system described above with ethylene and/orpropylene and/or one or more alpha olefins of formula CH₂═CHT¹, whereinT¹ is a C₂-C₂₀ alkyl radical; preferably propylene or ethylene. in orderto obtain a prepolymerized catalyst system preferably containing from 5to 500 g of polymer per gram of catalyst system;a-2) polymerizing propylene and optionally one or more monomers selectedfrom ethylene and alpha olefins of formula CH₂═CHT¹, wherein T¹ is aC₂-C₂₀ alkyl radical in the presence of the prepolymerized catalystsystem obtained in step a-1).

Step a) of the present invention can be carried out in liquid phase, inwhich the polymerization medium can be an inert hydrocarbon solvent orthe polymerization medium can be liquid propylene optionally in thepresence of an inert hydrocarbon solvent, and of ethylene or one or morecomonomer of formula CH₂═CHT¹, or step a) can be carried out in a gasphase. Said hydrocarbon solvent can be either aromatic (such as toluene)or aliphatic (such as propane, hexane, heptane, isobutane, cyclohexaneand 2,2,4-trimethylpentane).

Preferably the polymerization medium is liquid propylene. It canoptionally contain minor amounts (up to 40% by weight, preferably up to20% by weight, more preferably up to 5% by weight) of an inerthydrocarbon solvent or of one or more comonomer such as ethylene oralpha-olefins of formula CH₂═CHT¹.

Step a) can be carried out in the presence of hydrogen. The ratiohydrogen/propylene present during the polymerization reaction ispreferably higher than 1 ppm; more preferably it ranges from 5 to 2000ppm; even more preferably from 6 to 500 ppm with respect to thepropylene present in the reactor. Hydrogen can be added either at thebeginning of the polymerization reaction or it can also be added at alater stage after a prepolymerization step has been carried out. Thepropylene polymer obtained in step a) is a propylene homopolymer or apropylene copolymer containing up to 20% by mol preferably from 0.1 to10% by mol, more preferably from 1% to 5% by mol of derived units ofethylene or one or more alpha olefins of formula CH₂═CHT¹. Non-limitingexamples of alpha olefins of formula CH₂═CHT¹ which can be used in theprocess of the invention are 1-butene, 1-pentene, 4-methyl-1-pentene,1-hexene, 1-octene, 4,6-dimethyl-1-heptene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene. Preferredcomonomers are ethylene or 1-butene.

The amount of polymer obtained in step a) ranges from 5% to 39% byweight of the total polymer produced in the whole process, preferably itranges from 10% to 38% by weight of the total polymer produced in thewhole process; more preferably from 20% to 35% by weight of the totalpolymer produced in the whole process.

Preferably in step a) a propylene homopolymer or a propylene/ethylenecopolymer having an ethylene content lower than 10% by weight isprepared.

Step b) of the present invention can be carried out in liquid phase, inwhich the polymerization medium can be an inert hydrocarbon solvent orthe polymerization medium can be liquid propylene or ethylene optionallyin the presence of an inert hydrocarbon solvent, and of ethylene or oneor more comonomer of formula CH₂═CHT, or step b) can be carried out in agas phase. Said hydrocarbon solvent can be either aromatic (such astoluene) or aliphatic (such as propane, hexane, heptane, isobutane,cyclohexane and 2,2,4-trimethylpentane).

The polymerization temperature is generally comprised between −100° C.and +200° C., and, preferably, between 10° C. and +100° C. Thepolymerization pressure is generally comprised between 0.5 and 100 bar.The amount of polymer obtained in step b) ranges from 61% to 95% byweight of the polymer produced in the whole process, preferably itranges from 62% to 90% by weight of the polymer produced in the wholeprocess, more preferably it ranges from 65% to 80% by weight of thepolymer produced in the whole process.

Step b) can be carried out in the presence of hydrogen. The ratiohydrogen/hethylene present during the polymerization reaction ispreferably higher than 1 ppm with respect to the ethylene or propylene,depending on what is the prevalent monomer, present in the reactor; morepreferably it ranges from 5 to 2000 ppm; even more preferably from 6 to500 ppm.

In step b) an ethylene or propylene copolymer having from 4% by mol to90% by mol, preferably from 15% by mol to 60% by mol of derived units ofcomonomers of formula CH₂═CHT and optionally up to 20% of derived unitsof non conjugated diene, is produced. Examples of comonomer of formulaCH₂═CHT that can be used in step b) of the present invention other thenpropylene and ethylene are: 1-butene, 1-pentene, 4-methyl-1-pentene,1-hexene, 1-octene, 4,6-dimethyl-1-heptene, 1-decene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene.

In step b) of the present invention a propylene copolymer or an ethylenecopolymer can be produced. In case a propylene copolymer is produced,propylene is copolymerized with an alpha olefins of formula CH₂═CHT,wherein T is hydrogen or a C₁-C₁₀ alkyl radical, and optionally anon-conjugated diene, in the presence of the polymer obtained in step a)and optionally in the presence of an additional organo aluminumcompound; provided that an homopolymer is not produced; examples ofsuitable comonomers of formula CH₂═CHT are reported above; preferredcomonomer to be used with propylene are ethylene, 1-butene and 1-hexene.

In case an ethylene copolymer is produced ethylene is copolymerized withan alpha olefins of formula CH₂═CHT, wherein T is hydrogen or a C₁-C₁₀alkyl radical, and optionally a non-conjugated diene, in the presence ofthe polymer obtained in step a) and optionally in the presence of anadditional organo aluminum compound; provided that an homopolymer is notproduced; examples of suitable comonomers of formula CH₂═CHT arereported above; preferred comonomer to be used with ethylene are1-butene and 1-hexene.

The polymer obtained in step b) can optionally contains up to 20% by molof a non conjugated diene. Non conjugated dienes can be a straightchain, branched chain or cyclic hydrocarbon diene having from 6 to 20carbon atoms. Examples of suitable non-conjugated dienes are:

-   -   straight chain acyclic dienes, such as 1,4-hexadiene and        1,6-octadiene;    -   branched chain acyclic dienes, such as 5-methyl-1,4-hexadiene,        3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene and mixed        isomers of dihydro myricene and dihydroocinene;    -   single ring alicyclic dienes, such as 1,3-cyclopentadiene,        1,4-cyclohexadiene, 1,5-cyclooctadiene and 1,5-cyclododecadiene;    -   multi-ring alicyclic fused and bridged ring dienes, such as        tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene,        bicyclo-(2,2,1)-hepta-2,5-diene; and    -   alkenyl, alkylidene, cycloalkenyl and cycloalkylidene        norbornenes, such as 5-methylene-2-norbornene (MNB),        5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,        5-(4-cyclopentenyl)-2-norbornene,        5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene and        norbornadiene.

Preferred dienes are 1,4-hexadiene (HD), 5-ethylidene-2-norbornene(ENB), 5-vinylidene-2-norbornene (VNB), 5-methylene-2-norbornene (MNB)and dicyclopentadiene (DCPD). Particularly preferred dienes are5-ethylidene-2-norbornene (ENB) and 1,4-hexadiene (HD).

When present the non-conjugated dienes are generally incorporated intothe polymer in an amount from 0.1% to about 20% by mol; preferably from1% to 15% by mol, and more preferably from 2% to 7% by mol. If desired,more than one diene may be incorporated simultaneously, for example HDand ENB, with total diene incorporation within the limits specifiedabove.

The process of the present invention can be carried out in one reactoror in two or more reactor in series. Each step (step a and b) can becarried out in slurry, solution or in a gas phase; preferably step a iscarried out in slurry or in a gas phaseL; preferably step b) can becarried out in slurry or in a gas phase. However it is also possiblethat both steps are carried out in solution.

The following examples have an illustrative a non limiting purpose

EXAMPLES General Characterization

Intrinsic Viscosity (IV) in Decahydronaphthalene

The intrinsic viscosity in Decahydronaphthalene (DHN) was determined onan Ubbelohde viscometer PVS 1 with an S 5 measuring head (both fromLauda) in decalin at 135° C. To prepare the sample, 20 mg of polymerwere dissolved in 20 ml of decalin at 135° C. over a period of 2 hours.15 ml of the solution were placed in the viscometer; the instrumentcarried out a minimum of three running-out time measurements until aconsistent result had been obtained. The IV was calculated from therunning-out times according to IV=(t/t0−1)*1/c where t: mean of therunning-out time of the solution, t0: mean of the running-out time ofthe solvent, c: concentration of the solution in g/ml.

Intrinsic Viscosity (IV) in Tetrahydronaphthalene

The measurement for examples 1-5 were done in tetrahydronaphthalene(THN) solution obtained by dissolving the polymer at 135° C. for 1 hour.

Xylene Soluble Fraction at 25° C.

2.5 g of polymer were dissolved in 250 ml of o-xylene under stirring at135° C. for 30 minutes, then the solution was cooled to 25° C. and after30 minutes the insoluble polymer was filtered. The resulting solutionwas evaporated in nitrogen flow and the residue was dried and weighed todetermine the percentage of soluble polymer.

Melting Temperature Tm

Calorimetric measurements were performed by using a differentialscanning calorimeter DSC Mettler. The instrument is calibrated withindium and tin standards. The weighted sample (5-10 mg), was sealed intoaluminum pans, heated to 200° C. and kept at that temperature for a timelong enough (5 minutes) to allow a complete melting of all thecrystallites. Successively, after cooling at 20° C./min to −20° C. Afterstanding 5 minutes at 0° C., the sample was heated to 200° C. at a rateof 20° C./min. In this second heating run, the peak temperature wasassumed as melting temperature (Tm) and the area as the global meltinghentalpy (ΔH).

Gel Permeation Chromatography

Gel permeation chromatography (GPC) was carried out at 145° C. in1,2,4-trichlorobenzene using a GPC apparatus 150C from Waters. The datawere evaluated using the software Win-GPC fromHS-Entwicklungsgesellschaft fürwissenschaftliche Hard- und Software mbH,Ober-Hilbersheim. The calibration of the columns was carried out bymeans of polypropylene standards having molar masses of from 100 to 107g/mol. Mass average molar masses (Mw) and number average molar masses(Mn) of the polymers were determined. The Q value is the ratio of massaverage (Mw) to number average (Mn).

Chemicals and Characterization.

All chemicals were handled using standard Schlenk techniques.

Methylalumoxane (MAO) was received from Albemarle as a 30% wt/V toluenesolution and used as such and the silica was received from INEOS (ES70Y,100 microns).

-   Pseudo rac    Dimethylsilanediyl-(6-methyl-4-(4′-tert-butylphenyl)-1,2,3,5-tetrahydro-s-indacen-7-yl)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indenyl)-zirconium    dichloride (C-1) was synthesized according to PCT/EP2004/013827.

-   Pseudo rac    Dimethylsilanediyl-(6-methyl-4-phenyl-1,2,3,5-tetrahydro-s-indacen-7-yl)-(2-isopropyl-4-(4′-tert-butylphenyl)-1-indenyl)-zirconium    dichloride (C-2)

was synthesized according to PCT/EP2004/013827.

-   rac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tetr-butylphenyl)indenyl)zirconium    dichloride (C-3)

was prepared according to the procedure described in WO 01/48034.Preparation of Supported Catalyst System

6.3 g SiO₂ are placed in a round flask equipped with a KPG stirrer andsuspended at 0° C. in 30 ml toluene. Via a dropping funnel 15.1 ml MAOare slowly added at 0° C. After addition, the suspension is allowed tocome to room temperature (RT), and is then stirred for 2 h. The reactionmixture is placed in a stirred glass flask equipped with filter (sizeP3), where the solvent is filtered off. The residual is suspended in 20ml toluene, stirred for 15 min at room temperature, and filtered. Thesupport is suspended in 20 ml toluene, then brought to 80° C., andstirred for 30 min at this temperature before hot filtration. Again, thesupport is suspended in 20 ml toluene, then brought to 80° C., andstirred for 30 min at this temperature before hot filtration. TheMAO/silica is suspended at 15° C. in 20 ml toluene. Under stirring, asolution of 0.25 mmol (207 mg, 40 μmmol/g carrier) of the metalloceneindicated in table 1 in 2 ml MAO and 2 ml toluene is slowly added. Thereaction mixture is stirred for 1 h at 15° C., and after raising thetemperature to 40° C., again stirred for 2 h. Then, it is filtered. Theresidual solid is washed 3 times at 60° C. with 20 ml toluene each(stirring: 3×30 min). After the last filtration, the reaction product istransferred with some toluene into a glass frit (size P3), and filteredagain. The catalyst is transfer after drying at RT in high vacuum untilweight constant.

Polymerization Examples 1-3 Multistep Polymerization

Step a)

A 2.5 L autoclave, previously kept overnight under nitrogen purge, isadded with 2 mmol Triethylaluminum (TEA) (as 10% w/v hexane solution) asreactor scavenger. Also 0.5 bar-g of propylene are fed to prevent airinsertion in the reactor.

Prepolymerization: 252 g propylene are fed in the autoclave at 0° C. Thecatalytic system is injected in the reactor and propylene isprepolymerized at 30° C. for 5 minutes. At the end of this step thereactor temperature was raised from 30 to 70° C. (in 10 minutes). Duringthe temperature increase also 59 cc H₂ are fed, corresponding to 2.63mmol H₂.

Propylene polymerization in bulk this step is carried out at 30 bar-gpressure and 70° C. until the liquid propylene is totally consumed, andthe pressure inside the reactor starts to decrease. When this step iscompleted, the PP matrix polymerization time is recorded and thepressure is released down to 0.1 bar-g propylene; at the same time thetemperature decreases to 30° C.

Step b)

Ethylene and propylene at a molar ratioethylene(C2)/propylene(C3)+ethylene(C2) of 0.5 are fed in the reactor toreach the pressure of 21 bar-g then the temperature is raised to 60° C.and the ethylene/propylene mixture is fed at constant pressure until 232g of monomers are consumed.

Then the reactor is vented and cooled down to room temperature; thus,the reaction is stopped. The polymer is collected and dried at reducedpressure and 60° C.

The resulting polymer has been subjected to xylene extraction at 25° C.according to the procedure described above. The fraction of polymersoluble in xylene at 25° C. has been taken as the amount of ethylenepropylene copolymers produced in the process. The polymerization dataare reported in table 1.

Step a) Step b) Activity Activity Kg PP/g Kg EPR/g IV xs Met catalyst/catalyst/ C2_(EPR) X.S. dl/g Tm Ex Met mg hour hour % wt % wt THN C. ° 1C-2 118 1.3 2.9 23.8 66.6 2.06 155.7 2 C-1 120 2.4 4.0 25.4 65.3 1.75156.1 3* C-3 380 0.75 2.5 22.0 62.3 1.26 152.0 *comparative EPRpropylene ethylene polymer

Polymerization Example 4 Multistep Polymerization

Step a)

A 2.5 L autoclave, previously kept overnight under nitrogen purge, isadded with 2 mmol Triethylaluminum (TEA) (as 10% w/v hexane solution) asreactor scavenger. Also 0.5 bar-g of propylene are fed to prevent airinsertion in the reactor.

Prepolymerization: 134 g propylene are fed in the autoclave at 0° C. Thecatalytic system is injected in the reactor and propylene isprepolymerized at 30° C. for 5 minutes. At the end of this step thereactor temperature was raised from 30 to 80° C. (in 10 minutes).Propylene polymerization in gas phase: this step is carried out at 24bar-g pressure and 80° C. until 70 grams of propylene are consumed andthe pressure inside the reactor starts to decrease. When this step iscompleted, the PP matrix polymerization time is recorded and thepressure is released down to 0.1 bar-g propylene; at the same time thetemperature decreases to 30° C.

Step b) Ethylene and propylene are fed in the reactor at a molar ratio(ethylene (propylene+ethylene)) of 0.3 and the temperature is raised toreach the pressure of 21 bar-g and the temperature of 70° C. Then theethylene/propylene mixture is fed at constant pressure until 232 g ofmonomers are consumed.

Then the reactor is vented and cooled down to room temperature; thus,the reaction is stopped. The polymer is collected and dried at reducedpressure and temperature.

The results are reported in table 2

TABLE 2 Step a) Step b) Activity Activity Kg PP/g Kg EPR/g Met catalyst/catalyst/ C2_(EPR) X.S. IV X.S. Tm Ex Met mg hour hour % wt % wt THN C.° 4 C-2 124 0.9 3.0 12.6 67.1 2.1 n.a. EPR propylene ethylene polymer

1. A multistep process comprising the following steps: step a)polymerizing propylene and optionally at least one monomer selected fromethylene or alpha olefins of formula CH₂═CHT¹, wherein T¹ is a C₂-C₁₀alkyl radical, in the presence of a catalyst system comprising: i) atleast one metallocene compound of formula (I):

ii) an alumoxane or a compound that forms an alkyl metallocene cation;and optionally iii) a first organo aluminum compound, thereby forming apolymer in an amount; step b) contacting, under polymerizationconditions, propylene or ethylene with at least one alpha olefin offormula CH₂═CHT, wherein T is hydrogen or a C₁-C₁₀ alkyl radical, andoptionally a non-conjugated diene, in the presence of the polymerobtained in step a) and optionally in the presence of a second organoaluminum compound, provided that a homopolymer is not produced, therebyforming a polymer in an amount; wherein the amount of the polymerobtained in step a) ranges from 5% by weight to 39% by weight of thepolymer obtained in the whole process, and the amount of polymerobtained in step b) ranges from 61% by weight to 95% by weight of thepolymer obtained in the whole process; wherein in the compound offormula (I), M is an atom of a transition metal selected from thosebelonging to group 4 of the Periodic Table of the Elements; X, equal toor different from each other, is a hydrogen atom, a halogen atom, an R,OR, OR′O, OSO₂CF₃, OCOR, SR, NR₂ or PR₂ group wherein R is a linear orbranched, cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl, C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical,optionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements, and R′ is a C₁-C₂₀-alkylidene,C₆-C₂₀-arylidene, C₇-C₂₀-alkylarylidene, or C₇-C₂₀-arylalkylideneradical; L is a divalent bridging group selected from C₁-C₂₀ alkylidene,C₃-C₂₀ cycloalkylidene, C₆-C₂₀ arylidene, C₇-C₂₀ alkylarylidene, or aC₇-C₂₀ arylalkylidene radicals, optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements, or itis a silylidene radical containing up to 5 silicon atoms; R¹ and R¹⁹ aredifferent from each other and are a Z^(1′) or Z^(2′) group whereinZ^(1′) is an alpha branched C₁-C₂₀ hydrocarbon radical optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements, and Z^(2′) is a linear C₁-C₄₀ hydrocarbon radicaloptionally containing heteroatoms belonging to groups 13-17 of thePeriodic Table of the Elements, with the proviso that if R¹ or R¹⁹ areZ^(1′) then R¹⁹ or R¹ are Z^(2′); R² and R³, are part of 4-7 memberedring condensed to the benzene ring of the indenyl moiety, said ringoptionally containing heteroatoms belonging to groups 13-16 of thePeriodic Table of the Elements, the valence of each atom forming saidring is filled with R¹⁸ groups, wherein R¹⁸, equal to or different fromeach other, are hydrogen atoms or a C₁-C₄₀ hydrocarbon radical, saidring can be saturated or it can contain double bonds; R⁴ is a hydrogenatom or a C₁-C₄₀ hydrocarbon radical optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements; and Wis an aromatic 5 or 6 membered ring that can contain heteroatomsbelonging to groups 15-16 of the Periodic Table of the Elements, thevalence of each atom of said ring is substituted with hydrogen atom orit can optionally be substituted with R⁵ groups, wherein R⁵, equal to ordifferent from each other, are C₁-C₄₀ hydrocarbon radicals optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements; R²⁰, R²¹ and R²², equal to or different from eachother, are hydrogen atoms or C₁-C₄₀ hydrocarbon radicals optionallycontaining heteroatoms belonging to groups 13-17 of the Periodic Tableof the Elements.
 2. The multistep process according to claim 1 whereinin the compound of formula (I), X is a hydrogen atom, a halogen atom, aOR′O or R group; L is Si(R¹¹)₂, wherein R¹¹ is a linear or branched,cyclic or acyclic, C₁-C₄₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynyl,C₆-C₄₀-aryl, C₇-C₄₀-alkylaryl or C₇-C₄₀-arylalkyl radical; R⁴ is ahydrogen atom a C₁-C₁₀-alkyl or a C₆-C₄₀-aryl radical; R¹⁸ is a hydrogenatom or a linear or branched, C₁-C₂₀-alkyl radical; R² and R³, formtogether a condensed saturated 3-7 membered ring optionally containingheteroatoms belonging to groups 13-16 of the Periodic Table of theElements; and R²⁰ and R²¹ are hydrogen atoms or C₁-C₁₀ alkyl radicals,with the proviso that they are not both C₁-C₁₀ alkyl radicals.
 3. Themultistep process according to claim 1 wherein W is selected from themoieties of formula (Wa), (Wb) and (Wc):

wherein the * represents the point in which the moiety bonds the indenylmoiety of the compound of formula (I); R⁶, R⁷, R⁸, R⁹ and R¹⁰, equal toor different from each other, are hydrogen atoms or C₁-C₄₀ hydrocarbonradicals optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements; Z¹ is a nitrogen atom or a CR¹⁰group; Z² is a nitrogen atom or a CR⁶ group; Z³ is a nitrogen atom or aCR⁷ group; Z⁴ is a nitrogen atom or a CR⁸ group; Z⁵ is a nitrogen atomor a CR⁹ group; provided that not more that 2 groups among Z¹, Z², Z³,Z⁴ and Z⁵ are nitrogen atoms, Z⁶ is an oxygen atom, a sulfur atom, aNR¹³ group or a CR¹³ group; Z⁷ is an oxygen atom, a sulfur atom, a NR¹⁴group or a CR¹⁴ group; Z⁸ is an oxygen atom, a sulfur atom, an NR¹⁵group or a CR¹⁵group; Z⁹ is an oxygen atom, a sulfur atom, an NR¹⁶ groupor a CR¹⁶ group; Z¹⁰ is a nitrogen atom or a carbon atom that bonds theindenyl moiety of the structure of formula (I), with the proviso thatnot more than 1 group among Z⁶, Z⁷, Z⁸, Z⁹ or Z¹⁰ is a sulfur atom, anoxygen atom or a nitrogen-containing group atom selected from NR¹³,NR¹⁴, NR¹⁵, NR¹⁶, and a nitrogen atom; and R¹³, R¹⁴, R¹⁵ and R¹⁶, equalto or different from each other, are hydrogen atoms or C₁-C₄₀hydrocarbon radicals optionally containing heteroatoms belonging togroups 13-17 of the Periodic Table of the Elements.
 4. The multistepprocess according to claim 3 wherein, in the moiety of formula (Wa), R⁷is a C₁-C₄₀-alkyl radical, and R⁶, R⁸, R⁹ and R¹⁰ are hydrogen atoms. 5.The multistep process according to claim 3 wherein, in the moiety offormula (Wa), R¹⁰ and R⁸ are C₁-C₄₀-alkyl radicals and R⁷, R⁸ and R⁹ arehydrogen radicals.
 6. The multistep process according to claim 3wherein, in the moiety of formula (Wa), R⁶, R⁷ and R⁸ are linear orbranched C₁-C₄₀-alkyl radicals and R¹⁰ and R⁹ are hydrogen atoms.
 7. Themultistep process according to claim 3 wherein, in the moiety of formula(Wa), R⁶, R⁷, R⁸, R⁹ and R¹⁰ are hydrogen atoms.
 8. The multistepprocess according to claim 3 wherein in the moiety of formula (Wb), whenZ¹ is a nitrogen atom, Z², Z³, Z⁴ and Z⁵ are respectively CR⁶, CR⁷, CR⁸and CR⁹ or when Z³ is a nitrogen atom Z¹, Z², Z⁴ and Z⁵ are respectivelyCR¹⁰, CR⁶, CR⁸ and CR⁹ or when Z² is a nitrogen atom Z¹, Z³, Z⁴ and Z⁵are respectively CR¹⁰, CR⁷, CR⁸ and CR⁹.
 9. The multistep processaccording to claim 3 wherein in the moiety of formula (Wc), Z⁶ is anoxygen atom, a sulfur atom or an NR¹⁶ group, wherein R¹⁶ is aC₁-C₄₀-alkyl radical.
 10. The multistep process according to claim 1wherein Z^(1′) is a compound of formula of formula (II):

or an alpha branched aryl or arylalkyl radical containing from 2 to 20carbon atoms optionally containing O, N, S, P and Se atoms; wherein inthe compound of formula (II), R²³ and R²⁴, equal to or different fromeach other, are C₁-C₄₀ hydrocarbon radicals optionally containingheteroatoms belonging to groups 13-17 of the Periodic Table of theElements; R²⁵ is an hydrogen atom or it has the same meaning of R²³ andR²⁴; and Z^(2′) is a linear C₁-C₂₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀ alkynylradical, optionally containing heteroatoms belonging to groups 13-17 ofthe Periodic Table of the Elements.
 11. The multistep process accordingto claim 10 wherein R²³ and R²⁴ are C₁-C₂₀-alkyl, C₂-C₄₀ alkenyl, C₂-C₄₀alkynyl radicals, optionally containing heteroatoms belonging to groups13-17 of the Periodic Table of the Elements; R²⁵ is a hydrogen atom; andZ^(2′) is a linear C₁-C₁₀-alkyl radical.
 12. The multistep processaccording to claim 3 wherein the compounds of formula (I) have formula(III):

wherein R¹¹ and R¹², equal to or different from each other, are hydrogenatoms or C₁-C₄₀ hydrocarbon radicals optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements.
 13. Themultistep process according to claim 3 wherein the compounds of formula(I) have formula (IV):

wherein R¹¹ and R¹², equal to or different from each other, are hydrogenatoms or C₁-C₄₀ hydrocarbon radicals optionally containing heteroatomsbelonging to groups 13-17 of the Periodic Table of the Elements.
 14. Themultistep process according to claim 13 wherein W is a moiety of formula(Wa).
 15. The multistep process according to claim 1 wherein thecatalyst system is supported on an inert carrier.
 16. The multistepprocess according to claim 1 wherein step a) further comprises aprepolymerization step a-1).
 17. The multistep process according toclaim 1 wherein step a) and step b) are carried out in liquid phase,wherein the polymerization medium is an inert hydrocarbon solvent or thepolymerization medium can be liquid propylene optionally in the presenceof an inert hydrocarbon solvent, and of ethylene or one or morecomonomer of formula CH₂═CHT¹ or CH₂═CHT, or steps a) or b) can becarried out in a gas phase.
 18. The multistep process according to claim1 wherein step a) is carried out in the presence of hydrogen.
 19. Themultistep process according to claim 1 wherein the polymer obtained instep a) is a propylene homopolymer or a propylene copolymer containingup to 20% by mol of derived units of ethylene or one or more alphaolefins of formula CH₂═CHT¹.
 20. The multistep process according toclaim 19 wherein the polymer obtained in step a) is a propylenehomopolymer or a propylene/ethylene copolymer having an ethylene contentlower than 10% by weight.
 21. The multistep process according to claim 1wherein step b) is carried out in the presence of hydrogen.
 22. Themultistep process according to claim 1 wherein the polymer obtained instep b) is an ethylene or propylene copolymer having from 4% by mol to90% by mol, of derived units of comonomers of formula CH₂═CHT andoptionally up to 20% of derived units of non conjugated diene.
 23. Themultistep process according to claim 1 wherein in step b) propylene iscopolymerized with alpha olefins of formula CH₂═CHT, wherein T ishydrogen or a C₁-C₁₀ alkyl radical, and optionally a non-conjugateddiene, in the presence of the polymer obtained in step a) and optionallyin the presence of a second organo aluminum compound, provided that ahomopolymer is not produced.
 24. The multistep process according toclaim 1 wherein in step b) ethylene is copolymerized with an alphaolefins of formula CH₂═CHT, wherein T is hydrogen or a C₁-C₁₀ alkylradical, and optionally a non-conjugated diene, in the presence of thepolymer obtained in step a) and optionally in the presence of a secondorgano aluminum compound; provided that an homopolymer is not produced.25. The multistep process according to claim 1 wherein in step a) from10% to 38% by weight of the total polymer produced in the whole processis produced and in step b) from 62% to 90% by weight of the polymerobtained in the whole process is produced.
 26. The multistep process ofclaim 1, wherein R² and R³ are 5 or 6 membered rings, said ringoptionally containing heteroatoms belonging to groups 13-16 of thePeriodic Table of the Elements.
 27. The multistep process of claim 10,wherein the compound of formula (II) or the alpha branched aryl orarylalkyl radical containing from 2 to 20 carbon atoms optionallycontains O, N, and S atoms.